Track idler mount and recoil adjuster

ABSTRACT

The track idler yoke of an endless track mechanism has a pair of forwardly extending legs mounted in a pair of cylindrical bearing members and has a rear end acted on by a hydraulic actuator which is connected to a gas charged hydraulic accumulator by way of a counterbalance valve. The counterbalance valve includes a differential pressure valve whereby the hydraulic actuator resists recoil of the track idler at a pressure approximately 1,640 pounds per square inch greater than the pressure exerted by the accumulator to return the idler to its normal operating position.

United States Patent [19] Orr [ TRACK IDLER MOUNT AND RECOIL ADJUSTER[75] Inventor: Bobby J. Orr, Springfield, Ill.

[73] Assignee: Allis-Chalmers Corporation,

Milwaukee, Wis.

[22] Filed: June 7, 1972 [21] Appl. No.: 260,631

[52] US. Cl. 305/10 [51] Int. Cl B62d 55/30 [58] Field of Search 305/10,31, 32, 30

[56] References Cited UNITED STATES PATENTS 3,539,229 11/1970 Scully305/10 3,337,208 8/1967 Johansson 2,818,311 12/1957 Ashley 3,733,1075/1973 Cote 305/10 FOREIGN PATENTS OR APPLICATIONS 1,808,528 11/1968Germany 305/10 Attorney, Agent,

[4 1 Jan. 22, 1974 9/1955 Germany 305/10 8/1969 Great Britain 305/10Primary ExaminerDavid Schonberg Assistant ExaminerReinhard J. Eisenzopf0r Firm-Charles L. Schwab, Robert B. Benson, Kenneth C. McKivett [57]ABSTRACT The track idler yoke of an endless track mechanism has a pairof forwardly extending legs mounted in a pair of cylindrical bearingmembers and has a rear end acted on by a hydraulic actuator which isconnected to a gas charged hydraulic accumulator by way of acounterbalance valve. The counterbalance valve includes a differentialpressure valve whereby the hydraulic actuator resists recoil of thetrack idler at a pressure approximately 1,640 pounds per square inchgreater than the pressure exerted by the accumulator to return the idlerto its normal operating position.

10 Claims, 4 Drawing Figures 1 TRACK IDLER MOUNT AND RECOIL ADJUSTERBACKGROUND OF THE INVENTION BRIEF DESCRIPTION OF THE PRESENT 3 INVENTIONThe present invention mounts the forward legs of the yoke for the trackidler in a pair of slide type bearing members and the rear of the yokeis acted on by a hydraulic actuator. The hydraulic actuator is suppliedfluid pressure from a gas charged accumulator by way of a counterbalancevalve which resists recoil action of the idler with greater force thanis exerted to reposition the idler after recoil.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of an endlesstrack mechanism incorporating the present invention;

FIG. 2 is a partial top view of the mechanism shown in FIG. 1 withcertain parts broken away for purposes of illustration;

FIG. 3 is a schematic view of the hydraulic track adjusting mechanism ofthe present invention; and

FIG. 4 is a section view of a counterbalance valve employed in thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, an endlesstrack mechanism is illustrated in which a track frame 12 has mountedthereon a sprocket 14, an idler 16, track rollers 17 and a supportingroller 18, such components serving to drive and support an endless trackbelt 13. The sprocket 14 is rotatably supported on the track frame by abearing 19 and is driven by power means on the vehicle on which thetrack frame 12 is installed. The idler 16 is rotatably mounted on ashaft 20 pinned to a pair of forwardly extending legs 22, 23 of an idleryoke 21, the latter being shiftable longitudinally on the track frame 12to achieve proper track adjustment.

Referring also to FIG. 2, the forwardly extending legs 22, 23 of theidler yoke 21 have parallel'cylindrical ends 24, 26 which reciprocablyfit into cylindrical bearings 27, 28 rigidly secured to channel members29, 31 of the track frame 12. A cylindrical rear end 36 is formed on theidler yoke 21 in line with the idler and fits in fluid tight relationwith the cylindrical interior bore 40 of a cylinder 37. Thus, the yokeend 36 and the cylinder 37 comprise a single acting hydraulic actuator35 with a pressure chamber 51. The cylinder 37 is rigidly secured to thetrack frame 12. The hydraulic actuator 35 is supplied hydraulic fluidunder pressure by a gas charged hydraulic accumulator 38 by way of aconduit 39, a counterbalance valve 41, and a conduit 42. Additionally, arelief valve housing is mounted on the end of the accumulator 38 andincludes a relief valve 62 and a suitable pressure type grease fitting63 2 through which oil is pumped under pressure to adjust the track.

Referring to FIG. 3, the flexible bag 60 of accumulator 38 is normallyprecharged with nitrogen gas through fitting 64 to l,900 pounds persquare inch. When the accumulator 38 is in its bladder bottomed outposition as shown in FIG. 3, the hydraulic actuator 35 is positioned tocause the idler 16 to adjust the track 13 to its proper operatingcondition. The track 13 is normally maintained in a. nontensionedcondition in which it is actually sufficiently loose to dip slightlybetween the idler 16 and the support roller 18. In the properly adjustedposition of the track 13, the bag 60 of the accumulator 38 will bebottomed out, and thus the actuator 35 will normally not be urging thetrack forwardly so as to tension it, but rather the track will be drapedaround the idler and the thrust rearwardly by the idler yoke will bethat caused by the nontensioned track weight and forces acting upon itduring movement of the crawler tractor.

Referring also to FIG. 4, the counterbalance valve 41 includes a checkvalve 56 which offers only a slight resistance to flow of oil fromconduit 39 to the actuator 35. The check valve 56 prevents reverse flowthrough the passage 76. Thus, any return flow from the actuator 38during idler recoil will pass through passage 67 and a differentialpressure valve 59 which is biased by a suitable adjustable spring 61.The differential pressure valve 59 will open when a predeterminedpressure differential exists between the conduit 42 and the conduit 39.In the illustrated embodiment, the pressure differential is 1,640 poundsper square inch. Thus, with the accumulator having an initial prechargeof 1,900 pounds per square inch, initial rearward recoil movement of theidler yoke21 will be resisted by fluid pressure in line 42 of about3,540 pounds per square inch. A suitable commercially availablecounterbalance valve for use in the present invention is Model lBl2-P-6-30S made by Fluid Controls, Inc. of Mentor, Ohio.

Referring again to FIG. 3, the relief valve 62 is set for approximately4,000 pounds per square inch, thus providing some measure of safety torelieve pressure before the accumulator is subjected to an excessivestress.

In the illustrated embodiment of the invention, the idler yoke 21 has athree point support with the rear central support being combined withthe hydraulic actuator 35, thereby reducing components and cost. It willbe noted that the legs of the yoke 21 are disposed to place the pivotaxis 65 of the idler 16 above the axis of actuator 35. This designfeature permits the elevation of the idler to be adjusted by placing theyoke in valve 41 and accumulator 38. The plug 63 is replaced and thenthe accumulator is charged with nitrogen to 1,900 pounds per squareinch. The system is proportioned so that when the foregoing steps aretaken the hydraulic fluid will be forced from the accumulator and theidler will be in the correct forwardly shifted position to properlyposition the track. Little, if any, tension is actually placed on thetrack. Upon wear of the track, the idler 16 can be adjusted forwardly byadding hydraulic fluid to the system. This can be done by addinghydraulic fluid such as oil by a pressure gun connected to fitting 63.

The recoil circuit includes conduit 42, passages 66, 67, differentialpressure valve 59, passages 68, 69 and conduit 39. The pressure inchamber 71 of valve 41 is the same as the pressure in conduit 39 becauseof the axial bore 72 and opening 73 in the shiftable spool 74 of valve59. The spring 61 is sufficiently strong to require 1,640 pounds persquare inch pressure differential between conduit 42 and conduit 39before the flow control spool 74 will move to the left and open topermit flow of fluid from the actuator 35 to the accumulator 38.

The hydraulic circuit for reseting the idler following recoil includes abypass passage 76, interconnecting passages 76, 66 and one way flowcontrol means in the form of check valve 56. In some tractors it may bedesirable to provide a slower return of the idler following recoil andfor this purpose a restrictor 77 with a suitable orifice 78 can beincluded in passage 76.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In an endless track mechanism including a track frame and a trackidler rotatably mounted on a yoke connected to the track frame forrearward longitudinal recoil and adjustment relative thereto including arear end portion in line with said idler, a track recoil and adjustingsystem comprising:

a hydraulic actuator having cylinder and piston components, one of whichis secured to said track frame and the other of which is on a rear endportion of said yoke,

a gas charged hydraulic accumulator which is bottomed out during normaloperation of said track mechanism,

a differential pressure valve,

a conduit connecting said differential pressure valve to said actuator,

a conduit connecting said differential pressure valve to saidaccumulator, said differential pressure valve opening to pass hydraulicfluid from said actuator to said accumulator during recoil upon thepressure in said actuator exceeding the pressure in said accumulator bya predetermined amount,

a bypass circuit connected to said conduits in bypassing relation tosaid differential pressure valve,

a check valve in said bypass circuit permitting flow of hydraulic fluidfrom said accumulator to said actuator to adjust the idler forwardly,

orifice means in said bypass circuit effecting slow return of said idleryoke to its normal forward position after rearward recoil thereof, and

hydraulic relief valve means operatively associated with saidaccumulator operable to relieve pressure at a value substantially abovethe pressure at which said differential pressure valve opens, therebypreventing said accumulator from being subjected to excessive pressures.

2. The invention of claim 1 wherein said yoke includes a pair offorwardly extending legs having parallel cylindrical ends and furthercomprising a pair of cylindrical bearing members secured to said trackframe in which said cylindrical ends are reciprocably mounted forlongitudinal movement.

3. The invention of claim 2 wherein said piston is integrally formed onthe rear end of said yoke.

4. The invention of claim 3 wherein the axis of said piston ishorizontally spaced from the plane defined by the axes of saidcylindrical forward ends of said yoke.

5. Means for mounting an idler on a frame for an endless beltcomprising:

a yoke rotatably carrying said idler and having forwardly extending legspresenting parallel cylindrical ends, respectively, and a rearwardlyextending portion having a cylindrical end part,

a pair of cylindrical bearing means on said frame reciprocablysupporting said parallel cylindrical ends, and

a support element on said frame having a cylindrical surface incooperative engagement with said cylindrical end part, the axis of saidcylindrical end part being spaced from the plane defined by the axes ofsaid parallel cylindrical ends.

6. The invention of claim 5 wherein said cylindrical surface is aradially inward facing surface.

7. The invention of claim 6 wherein said support element is a cylinderof a hydraulic actuator.

8. The invention of claim 5 wherein said support element is a componentofa single acting hydraulic actuator operable to adjust the longitudinalposition of said yoke.

9. The invention of claim 8 wherein said component is a cylinder andsaid cylindrical end part is a piston.

10. In an endless track mechanism including a track frame and a trackidler rotatably mounted on a yoke connected to the track frame forrearward longitudinal recoil and adjustment relative thereto including arear end portion in line with said idler, a track recoil and adjustingsystem comprising:

a pair of forwardly extending legs on said yoke having cylindrical ends,

a pair of cylindrical bearing members secured to said track frame andreciprocably mounting said cylindrical ends for longitudinal movement,

a hydraulic actuator having a cylinder secured to said track frame and apiston component integrally formed on the rear end of said yoke, theaxis of said piston component being horizontally spaced from the planedefined by the axes of said cylindrical forward ends of said yoke,

a gas charged hydraulic accumulator which is bottomed out during normaloperation of said track mechanism,

a differential pressure valve,

a conduit connecting said differential pressure valve to said actuator,

a conduit connecting said differential pressure valve to saidaccumulator, said differential pressure valve opening to pass hydraulicfluid from said actuator to said accumulator during recoil upon thepressure in said actuator exceeding the pressure in said accumulator bya predetermined-amount,

a bypass circuit connected to said conduits in bypassing relation tosaid differential pressure valve,

a check valve in said bypass circuit permitting flow of hydraulic fluidfrom said accumulator to said actuator to adjust the idler forwardly,and

hydraulic relief valve means operatively associated with saidaccumulator operable to relieve pressure at a value substantially abovethe pressure at which said differential pressure valve opens, therebypreventing said accumulator from being'subjected to excessive pressures.

1. In an endless track mechanism including a track frame and a trackidler rotatably mounted on a yoke connected to the track frame forrearward longitudinal recoil and adjustment relative thereto including arear end portion in line with said idler, a track recoil and adjustingsystem comprising: a hydraulic actuator having cylinder and pistoncomponents, one of which is secured to said track frame and the other ofwhich is on a rear end portion of said yoke, a gas charged hydraulicaccumulator which is bottomed out during normal operation of said trackmechanism, a differential pressure valve, a conduit connecting saiddifferential pressure valve to said actuator, a conduit connecting saiddifferential pressure valve to said accumulator, said differentialpressure valve opening to pass hydraulic fluid from said actuator tosaid accumulator during recoil upon the pressure in said actuatorexceeding the pressure in said accumulator by a predetermined amount, abypass circuit connected to said conduits in bypassing relation to saiddifferential pressure valve, a check valve in said bypass circuitpermitting flow of hydraulic fluid from said accumulator to saidactuator to adjust the idler forwardly, orifice means in said bypasscircuit effecting slow return of said idler yoke to its normal forwardposition after rearward recoil thereof, and hydraulic relief valve meansoperatively associated with said accumulator operable to relievepressure at a value substantially above the pressure at which saiddifferential pressure valve opens, thereby preventing said accumulatorfrom being subjected to excessive pressures.
 2. The invention of claim 1wherein said yoke includes a pair of forwardly extending legs havingparallel cylindrical ends and further comprising a pair of cylindricalbearing members secured to said track frame in which said cylindricalends are reciprocably mounted for longitudinal movement.
 3. Theinvention of claim 2 wherein said piston is integrally formed on therear end of said yoke.
 4. The invention of claim 3 wherein the axis ofsaid piston is horizontally spaced from the plane defined by the axes ofsaid cylindrical forward ends of said yoke.
 5. Means for mounting anidler on a frame for an endless belt comprising: a yoke rotatablycarrying said idler and having forwardly extending legs presentingparallel cylindrical ends, respectively, and a rearwardly extendingportion having a cylindrical end part, a pair of cylindrical bearingmeans on said frame reciprocably supporting said parallel cylindricalends, and a support element on said frame having a cylindrical surfaceiN cooperative engagement with said cylindrical end part, the axis ofsaid cylindrical end part being spaced from the plane defined by theaxes of said parallel cylindrical ends.
 6. The invention of claim 5wherein said cylindrical surface is a radially inward facing surface. 7.The invention of claim 6 wherein said support element is a cylinder of ahydraulic actuator.
 8. The invention of claim 5 wherein said supportelement is a component of a single acting hydraulic actuator operable toadjust the longitudinal position of said yoke.
 9. The invention of claim8 wherein said component is a cylinder and said cylindrical end part isa piston.
 10. In an endless track mechanism including a track frame anda track idler rotatably mounted on a yoke connected to the track framefor rearward longitudinal recoil and adjustment relative theretoincluding a rear end portion in line with said idler, a track recoil andadjusting system comprising: a pair of forwardly extending legs on saidyoke having cylindrical ends, a pair of cylindrical bearing memberssecured to said track frame and reciprocably mounting said cylindricalends for longitudinal movement, a hydraulic actuator having a cylindersecured to said track frame and a piston component integrally formed onthe rear end of said yoke, the axis of said piston component beinghorizontally spaced from the plane defined by the axes of saidcylindrical forward ends of said yoke, a gas charged hydraulicaccumulator which is bottomed out during normal operation of said trackmechanism, a differential pressure valve, a conduit connecting saiddifferential pressure valve to said actuator, a conduit connecting saiddifferential pressure valve to said accumulator, said differentialpressure valve opening to pass hydraulic fluid from said actuator tosaid accumulator during recoil upon the pressure in said actuatorexceeding the pressure in said accumulator by a predetermined amount, abypass circuit connected to said conduits in bypassing relation to saiddifferential pressure valve, a check valve in said bypass circuitpermitting flow of hydraulic fluid from said accumulator to saidactuator to adjust the idler forwardly, and hydraulic relief valve meansoperatively associated with said accumulator operable to relievepressure at a value substantially above the pressure at which saiddifferential pressure valve opens, thereby preventing said accumulatorfrom being subjected to excessive pressures.